Aqueous dispersion of carbon black



Patented July 7, 1936 I Q 2,0 ,75

hurrah srars OFFHCE 2594:6357 AQUEQUS DISPERSION F CARBON BLACK Georgelit. Tucker, North Andover, Mass; @harles W. Tucker, administrator ofsaid George R. Tucker, deceased, assignor to Dewey and Almy Ghemicai@ompany, Cambridge, Mass, a corporation of Massachusetts No Drawing.Application November 23, 1932, Serial No. 644,658?

.14 (Claims. (or. 13%58) This invention relates to the dispersion ofcaralbumen. While these agents are generally very bon black in anaqueous medium, and generally efiective to disperse most finely dividedpigments comprises the use of a dispersing agent of, the in water,carbon black presents unusual difilculgeneral structure obtained bycondensing an aroties and is not particularly well dispersed by them.

matic sulfonic acid, or a derivative thereof, with This is believed tobe due to the fact that car- 5 formaldehyde, or its equivalent, aprocess and a hon black particles are very much smaller than, productthereof, all as hereinafter more fully in fact of a difierent order ofmagnitude from described and claimed. that-of, the particles of ordinarypigments. Fur- There are many industrial applications of carthermore,soaps and proteins are in themselves bon black which require itssuspension or disperattended with certain disadvantages. In order 10sion in an aqueous medium. Thus, for examto be efiective they must beused in relatively ple, it is frequently used as a pigment in thepreplarge quantities; and, furthermore, they lose their 'ar'ation ofblack paper or paper-like materials in eifectiveness and areprecipitated when brought which case the carbon black may be slurrieolin in contact with acid environments or the ions of water and added as apaste or thin slurry to heavy metal salts. The latter disadvantages ren-15 the stock in a paper beater. In this manner carder soaps or proteinsparticularly ineffective to bon black is commonly added to aqueousslurries disperse carbon black in water for use in cement of asbestoswhich are to be used for the manuor mortar; or in paper-making when anacid or facture of asbestos board, gasket materials, and alum size isemployed; or for use with aqueous an the like. Aqueous dispersions ofcarbon black are slurries of asbestos such as are commonly encoun- 2Qfrequently added to rubber latex to provide a comtered in themanufacture of asbestos board, gaspounding and pigmenting agent for therubber ket material, and the like, which slurries, owing constituentthereof. Black concrete or cement is to theinherent chemical nature ofthe asbestos,

commcnly prepared by mixing carbon black with always contain calcium andmagnesium ions. v

2 the cement or mortar when in the wet state. Similarly, dispersions ofcarbon black in water Furthermore, it has been proposed, and theprepared with the aid of soaps or proteins are also process presentsmuch promise, to use a disperespecially ineffective for use inconnection with sion of carbon black in an aqueous medium as a thegeneral process described in my Patent No. printing ink in place of theprinting inks ordi- 1,9 ,05 ssued Ap 1934, in Which 0 narily usedconsisting of carbon black and a tery slurry of asbestos is treated withan aque us so suitable oil. dispersion of electropositive rubberparticles The dispersion of carbon black in water prewhich dispersionmay be acid in reaction or may sents difficulties, however, and thesedificulties contain polyvalent metal ions. have militated against itsmore general and oth- An object of this invention is to provide asuserwise advantageous use. If carbon black is pen n of Carbon black inWater in which the 35 stirred into water, it will be found that theparcarbon black is more completely dispersed and ticles are not readilywet by the water and, once which therefore possesses greater tinctorialpow-. wetted, they tend to cling together, i. e. agglomer than hasheretofore been possible. Another erate, and do not disperse in theaqueous medium object of the invention is to provide a. disperascolloidal particles of carbon black. sion of carbon black in water whichis not readily 40 These non-wetting and non-dispersing characa gregatted by acids or polyvulent teristics constitute serious disadvantages inthe metal ions such as are provided by the acid sizes practical use ofcarbon black when suspended in employed in paper-making; by the asbestosof water because carbon black is generally used for asbestos-water'slurries emp yed n the manuits tinctorial power; and, as is well knownand facture of asbestos board, gasket material, and 45 recognized, thetinctorial power of a finely di- .the like; by the heavy metal ionsencountered in vided material is proportional to the size of theordinary cement or mortar; or by the electroindividual particles and thecompleteness with positive rubber dispersions employed in the genwhichthey are dispersed. eral process described in my before mentionedAttempts have been made to overcome the Patent No. 1,956,053, issuedApril 24, 1934. Still 50 stateddifilculties by adding certain protectivecol-' another object of the invention is to provide loids to the waterin which the carbon black was aqueous carbon black dispersions ofgreater conto be suspended. Forthis purpose therehavebeen centration andgreater fluidity or plasticity at a employed soaps, such as sodiumstearate or olegiven high concentration than has heretofore ate, andproteins, such as casein, hemoglobin, or been attainable. Other objectsand advantages 55 more convenient and commercially practical, by

bons or their derivatives, with formaldehyde or its equivalent. Thesecompounds may be looked upon as derivatives of polyaryl alkyls or theirhomologues and may be expressed by the general graphical formula(A-RA')SO3M in which A and A designate two or more aromatic groups whichmay or may not be alike; which are joined to an aliphatic nucleus Rwhich may consist of a single alkyl group or a plurality of alkyl groupsassociated in straight chain or branched chain formation; and in which$03M designates at least one solubilizing group such as the freesulfonic acid group or a sulfonic acid group in combination with asoluble salt-forming radical. The members of the class may besynthesized either by direct sulfonation of a hydrocarbon or aderivative thereof which possesses the necessary configuration of atleast two aromatic nuclei joined to an aliphatic nucelus, ones isusually causing an aromatic sulfonic acid or a derivative thereof toreact with formaldehyde or its equivalent, preferably in the ratio ofapproximately two mols. of aromatic sulfonic acid for each mol ofaldehyde. The member of the family which i prefer to employ because itis cheap and very effective for present purposes may be obtained bycondensing beta-naphthalene sulfonic acid with formaldehyde. While thebeta-naphthalene sulfonic acid condensation product may be preparedinknown ways, I find that the product obtained by the followingprocedure possesses highly satisfactory properties for use in practicingmy invention. 1

To 100 parts of concentrated sulfuric acid (specific gravity 1.84)contained in a suitable sulfonator and maintained at 160 C. are addedslowly with stirring 100 parts of refined naphthalene. After all of thenaphthalene has been in troduced (this operation generally requiresabout one hour), the mass is stirred at 160 C. for four hours longer oruntil a test shows that substantially none of the naphthalene remainsunsuifonated. The sulfonation mixture is then cooled to about 100 C.and-diluted with 44 parts of water to prevent solidification onsubsequent cooling. The diluted material is further cooled to C. atwhich temperature 12 parts of a 40% aqueous solution of formaldehyde areadded. This mixture is then. stirred for three hours longer at 80 C.;but at the end ofeach successive hour there are added 12 parts more offormaldehyde solution, making a total at the end of the three hours offour portions or 48 parts in all. After all the formaldehyde, has beenadded, the temperature is progressively raised over a period of one hourto -100 0. where it is maintained for 18 hours, while the mass isconstantly stirred, or until the control test described later on in thisspecification shows that a product of optimum effectiveness has beenobtained. Experience has shown that when pure naphthalene is used, afinal heating period of 18 hours yields the best product. Soon after thetemperature has been raised to 95-100 C., it is found that substantiallynone of the aldehyde remains unconsumed in :the condensation reaction.During the later stages of the 18-hour heating period, the mixtureprogressively thickens until at the end it generally reachesthe-consistency of thick molasses; If this thickening becomes so great,

however, as to prevent proper stirring, a small quantity of water may beadded to keep the material liquid. After the heating is completed, themixture is cooled, neutralized with a suitable alkali, e. g. sodiumhydroxide, and, if desired, dried; It is then ready for use.

A somewhat purer and better product can be obtained by diluting theviscous reaction mass with about three times its volume of water. (theamount is not important so long as it is sumci'ent to permit convenienthandling in the subsequent filtering operation), and neutralizing withlime.

lime. The neutralized slurry is filtered hot to remove the calciumsulfate precipitate which forms from the interaction of the lime andsulfuric acid unconsumed in the sulfonation reaction; and to thefiltrate is added the requisite amount or. sodium carbonatequantitatively to convert the calcium salt of the desired sulfonic acidinto its sodium salt. The resulting calcium carbonate precipitate maythen be removed by filtration and the filtrate which contains thedesired ingredient evaporated to dryness according to any of the wellknown drying procedures.

The sulfonation of the naphthalene may be conducted in a cast ironvessel; but the reaction with formaldehyde is preferably carried out in3 enameled or lead-lined apparatus.

In place of naphthalene in the foregoing sulfonation and condensationprocedure may be employed, as more fully described in the previouslymentioned Patent No. 1,956,053, issued April 2 1934, any aromatichydrocarbon such as benzene, diphenyl, anthracene, phenanthrene,fiuorene, etc, or any homologue or derivative thereof. When suchsubstitutions are made, however, it is generally necessary to modify thesulfonation andcondensation procedure; but these. modifications, whichvary with each compound, will be apparent to those skilled in the art.Products derived from the benzene series, however, are less effectivethan materials derived from polynuclear aromatic hydrocarbons or theirderivatives. Alkylated aromatic compounds such, for example, as affordedby the sulfonic acids of xylene, cumene, ethyl naphthalene, or retenegenerally lead to products which are more effective than similar butunsubstituted compounds. Thus the condensation product obtained fromxylene sulfonic acid is more effective for present purposes than the oneobtained from thesimpler benzene derivative. But whereas condensationproducts prepared from alkylated compounds are especially desirable foruse in the broader aspects of this invention, they may be objectionablefor some purposes because, due to their tendency to reduce the surfacetension of water, they promote the formation of 'foam in the carbonblack dispersion. Materials made from aromatic compounds which are freefrom substituting alkyl groups have substantially no tendency to reducethe surface tension of water; and for this reason carbon blackdispersions prepared with them do not have the undesirable tendency toform foam possessed by aqueous dispersions of carbon black prepared withthe aid of prior agents which, un-

For the latter purpose I generally use any aqueous paste or suspensionof hydrated or slaked like present materials, generally rely for their75 i'ace tension of water. 'i'he product obtained as described above bythe reaction of naphthalene sulfonic acid with formaldehyde isspecifically recommended for use in a preierredform or this inventionwhere the tendency to produce foam is objectionable.

In the chemical reaction which occurs between an aromatic sulfonic acidand formaldehyde or its equivalent, it is my theory that the initialcondensation reaction is followed by a progressivepolymerization of theresulting condensed material, and that a certain optimum molecularweight is necessary to yield the best results for present purposes asdetermined according to the indicated empirical test-given later on inthis specification; but this theory forms no part of my dennition and Ido not desire to be bound by it.

Whereas I generally use the suli'onic acids ofthe herein defined classin the form of their sodium salts, any water-soluble salt or derivative,

or even the free-acid, may be employed. Salts of monovalent metals,particularly the alkali metals, are preferable, however, to salts ofpolya solution should be used for preparing the mixture winch contains aquantity of dispersing agent equal to about 4% of the weight of thecarbon black employed... in this connection, however, it may be saidfurther that different kinds of carbon black require differentquantities of dispersing agent under otherwise like conditions toproduce an optimum dispersing efiect. With most carbon blacks theoptimum dispersing efiect will be obtedned when a quantity of dispersingagent equal to 245% of the weight of carbon black is employed; but somesamples, 1. e. those of extremely small particle size, require a minimumof 4-8% to produce the best results. It is believed that the relativequantity of dispersing agent essential to produce a given result isdependent on the size and/or specific surface'ot the carbon blackparticles" to be dispersed. This is in accord with the observation thata thermatomirb carbon black which possesses an ultra-microscopicparticle size requires, for a unit weighta larger quantity of dispersingagent to produce a given result than does a carbon black known to bootlarger particle size. If a larger quantity oi dispersing agent isemployed than that necessary to produce the optimum result with anygiven carbon black, the excess of dispersing agent does no material harmbut is of no advantage. The

minimum quantity of agent required to produce the optimum result may 13be determined by trial. For example, 25-gram portions of the carbonblack to be tested may be vigorously stirred into 'lfi-cubic-centimeterportions of solutions containing, respectively, V 1, 1 and 2 grams ofthe dispersing agent. The minimum quantity of agent essential to producea paste having the maximum fluidity or least viscosity should .bechosen. As previously stated, this testis also useful to ascertain-andcontrol the optimum degree of polymerization of products made accordingto ins the carbon black with a. solution of the dispersing agent, carbonblock may be mixed with the dispersing agent in the dry and powderedstate and the resulting dry mixture may bestlrred into water or anaqueous medium, the dispersing agent dissolving in the watery liquor toprovide the desired peptizing influence. While this process hasadvantages for some purposes, it does not, however, give as good aresult as is obtained by mixing the carbon black into a previouslyprepared solution of dispersing agent; and it is necessary to use a-relatively larger quantity of dispersing agent toproduce in like degreethe dispersing efiect that would be obtained by stirring the carbonblack into a solution containing a lesser uantity of dissolveddispersing agent.

en it is desired to produce relatively dilute dispersions oi carbonblack in water, it is. usually desirable first to prepare a dispersionor the carbon black in high concentration and then to dilute with. waterto the desired value. This procedure is preferable both when the carbonblack is stirred into a solution of the dispersing agent and when a drymixture of carbon black and dispersing agent is added to water.

Carbon black dispersions prepared in accord ance with the presentinvention are more fluid or plastic than dispersions similarly preparedbut with the aid of no or other dispersing agents known to me. In thisconnection it may be said 3 that difierent carbon blacks dispersed in anaqueous medium give dispersions exhibiting widely difierentconsistencies at any given concentra tion. The process oi the presentinvention will always yield, however, so far as I am aware, a dispersionpossessing greater fluidity or plasticity at any given concentrationthan can be obtained under like conditions with other dispersing agents.Dispersions of ordinary carbon black preparedin accordance with thepresent invention and containing as much as 25% by weight of dispersedmaterial are quite fluid. Dispersions containing between and of carbonblack are of more or less plastic or pasty consistency. However, it ispossible with some carbon blacks to prepare in accordance with thepresent invention dispersions containing from 40 to 50% of dispersedmaterial which are of a smooth, pasty consistency. In

the absence of, any dispersing agent, or in the presence of mostdispersing agents, it is not gen- 5 orally possible to'go beyond 25-30%of carbon black without obtaining a dry crumbly product.

If a carbon black dispersion prepared in acw cordance with the presentinvention is diluted with water and examined under the microscope v at ahigh magnification (900 diameters), minute particles will be observedsuspended in the watery medium and engaging in rapid Brownian motion. Incontradistinction to dispersions generally prepared with the aid ofother dispersing agents, it will be found that the addition of smallquantities. oi acids, or of salts providing heavy metal ions, to carbonblack dispersions prepared according to the present invention will notmarkedly aggregate or flocculate the dispersed particles thereof. Thisfact makes the process ofthis invention particularly valuable fordispersing carbon black in acid environments or in the presence of heavymetal ions normally coagulative or colloidally dispersed material.

1. The process of dispersing carbon black in an aqueous medium whichcomprises agitating carbon black in an aqueous solution of a dispel-sing agent obtained by condensing lormoldoliyde with an aromatic sulfonicacid, whereby deflecculotion of the normally segregated particles ofcarbon black occurs, said agent teing present in amount of substantially2 to 8% hosed on the weight of the dry carbon block. t;

2. The process oi dispersing carbon clock. in on equeons medium whichcomprises agitating cosbon clock in on aqueous solution of e, agentootoineol by condensing formaldehyde with a polymuclesr aromaticsulfonic acid, whereby clefioccuieslon of the normally aggregatedparticles of carbon clock occurs, sold scent being present 7 in amountcl substantially 2 to 8% loosed on the weight oi carbon block. 3, Theprocess of dispersing corlcon lolsolz an aqueous medium which comprisesagitating on aqueous solution oi o. disnerse, plurality oi amnioticnuclei ing agent joined to s, methylene nucleus, whereby deiloe culetlonof normally aggregated particles of carbon blscl: occurs, solcl agentbeing nresent in amount cl substoutlolly 2 to 3% based on tie weight ofthe airy carbon black.

4. The process of dispersing carbon lolocl: in on aqueous inecl'um whichcomprises agitating carbon Toieiclz in en'oqueous solution of adispersing agent comprising it salt of a sultonic acid compound leavinga plurality of polynucleor er o mat-lo nuclei joined to a methylenenucleus. whereby defiocculstlon of the normallyaggregoted por ticies ofcartoon block occurs, said agent being present in amount ofsubstantially 2 to 8% based,

. on the weight of the dry carbon black.

5. As a new composition of matter, an oqueous dispersion of carbon blackwhich contains dissolved in the aqueous medium a dispersing scentobtained by condensing formaldehyde on aromatic sultonio acid, ssidagent being present in amount of substantially 2 to 8% based on theweight of the dry carbon block.

7 6. As a'new composition of matter, dry carbon black in intimateadmixture with substantially 2 to 8% loosed on the weight of the drycarbon black of a water-soluble dispersing agent obtained byccndensingformaldehyde with an aromatic soltonic acid. 4

7. As a new composition of matter, an aqueous dispersion of carbon blackwhich contains dis-. solved in the aqueous medium a dispersing agentpolynuclear aromatic sulionic acid, said agent being present in amountof substantially 2 to 8% loesezl on the weight of the dry carbon black.

ll, m s new composition of matter, dry carbon 10 black in intimate odurewith substantially 3 to 8% based on the weight of the dry carbontale-cl: of s, o ster-soluble dispersing agent obtained nrolneticsulfonic sold.

it. As :2, new composition oi matter, an aqueous dispersion of carbonblock which contains dissolved in the mucous medium dispersing agentlooming o piinolity of aromatic nuclei joined to a.

by o1rs-rlensing formaldehyde with. o polynuclear obtained by condensingformaldehyde with;

methylene nucleus, sold agent losing present in amount oi sucstnntlclly2 to 3% loosed on the weight of the dry cot-lion black.

lo. As s new composition oi matter, dry cocoon lei-eel; in admixturewith mtstsnllolly 2 to 8% on the weight oi tine dry cnrlson Toloclz oi owotemsoluole dispersing agent hiilli'llllgjit plurolity oi Monasticnuclei joined to nicthylenc nucleus.

- ll. .418 comomitlon oi matter, on aqueous dispersion of cmlson loloclzwhich contains solved in cocoons medium s dispersing agent comprising atsuifonic ocicl compound. o plurality of aromatic nuclei joined to amethylene nucleus, sold being present in amount oil substantially 2 toloosed on the weight of the l cocoon lolcog,

As new eomcosltlon of matter, m Sm-mm in intimate odimxture' 2 to 8%loosed on the weight of the dry cocoon block of o 'GfEtiJEP-Slilllllfisulionic acid dispersing scent o plucsllty oi aromatic nuclei gcinocl too methylene nuclew.

13. A water dispersslole carbon block mixturecomyorlsing o toasty massof carbon block, water in amount to produce o nests, and 2 to 8% besezlon the weiglit oi the dry carbon black of 9. dis-- pens-lug scentcomprising the formaldehyde con densetion pro-duct of o sulphoneteclsromotic com pound, sold pesto mixture upon dilution with water havingthe cot-lion blaclrpnrtlcles in colo0 loidelly dispersed condition.

it. A water dispersoble' carbon black mixture comprising as plastic messof carbon black, woter in smount to produce a plastic mixture, and 2 to3% loosed on the weight of the dry carbon black oi e, dispersing agentcomprising the formololeliyde condensation product of a sulpliouateclaromatic compound, said plastic. mixture upon dilution with water havingthe carbon black particles in colloldclly dispersed condition.

GEORGE E. TU.,

